It is well known in the integrated circuit manufacturing industry that a dielectric, such as silicon dioxide (SiO2), can be etched using hydrofluoric acid (HF). A typical etchant is buffered hydrofluoric acid (BHF; sometimes referred to as a buffered oxide etchant or BOE) that contains HF and an ammonium fluoride buffer (NH4F) to control etch rate and pH. BHF is widely used because it is very selective, i.e., the rate HF etches dielectric is several orders of magnitude greater than HF etches silicon (Si). Because the silicon is essentially unaffected by HF, a silicon surface exposed by the removal of an overlying dielectric is clean and free of etch-induced defects. However, with the substitution of copper for aluminum as the metal used to make conductors in integrated circuits, etching the dielectric with embedded copper conductors using an HF-containing etch results in the silicon surface having etch-induced damage or defects known as etch pits. These undesirable defects are believed to be a result of copper ions in the etchant which alter the silicon surface, making the surface susceptible to attach by HF. Unfortunately, the formation of etch pits may hinder the development of low-cost silicon-based microelectromechanical system (MEMS) devices, such as optical switches having arrays of movable silicon mirrors, because etch pits in mirror surfaces scatter reflected light.